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Lower power TL494, MC33063 etc.?

Discussion in 'Electronic Components' started by Joerg, Apr 21, 2007.

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  1. Joerg

    Joerg Guest

    Guess we all have used those staples. Those kinds are about the only
    cheap PWM chips when it comes to voltages above logic levels. However,
    unfortunately they were designed before the energy crisis and need lots
    of quiescent current. Is there anything available or maybe in design
    with the following specs:

    a. buck, or multi-mode
    b. internal switch
    c. <<1mA quiescent
    d. 7-40V input
    e. ahem, as usual: <40c a pop in qties

    I found tons of suitable devices but they all failed requirement "e",
    big time.
  2. legg

    legg Guest

    Output current rating of the internal switch?

  3. Joerg

    Joerg Guest

    That can be well under 100mA. It's for low power apps. Most of the
    modern versions have surprising current capabilities. It's just that
    they are priced way outside my usual wiggle room.
  4. legg

    legg Guest

    For a low power application jelly-bean, the last thing you'd
    intentionally impose on a device is a high input voltage. In that case
    you'd be looking for methods to cut the thing off completely, when not
    needed and to bootstrap the control supply when it's running.

    For < 1mA quiescent high voltage operating current, I don't see an
    integrated buck regulator below 1.25. (lm5009)

    LM2574, with a built-in shutdown capability, is 0.75. There are many
    others like it.

    At 100ma you could probably bodge something in any particular
    application. Isn't that what the high-priced help is for?

    If you could get by with buck-boost, using the positive input as the
    ground connection, there are a host of commodity low power HV
    integrated switchmode controllers that might be re-applied between 15
    and 40V. The control inversion generally puts people off.

  5. Joerg

    Joerg Guest

    Yep, it usually is. But most of the time that help leads to a discrete
    solution. Looks like it does again this time. It's hard to beat 1.5c
    transistors and 0.3c resistors, even when there are a lot of them.

    Oh, that wouldn't put me off at all. I love unorthodox solution, at
    least in electronics ;-)
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